Short-range communication equipment, such as Near Field Communication (NFC) transceivers are becoming more prominent in a wide variety of mobile digital devices, such as cellular phones, personal digital assistants, pagers and other mobile devices. The NFC transceivers provide the devices with the ability to communicate via RFID, Bluetooth®, infrared, Ultra Wideband or other types of near field communication dependent upon the type of transceiver associated with the mobile device. Continuous active operation of any type of short-range communication equipment, such as, for example a NFC system, however, consumes significant amounts of power. Power is consumed at high rates because NFC systems, such as RFID readers, read passive transponders, also referred to as “tags”, which have no battery of their own. As such, the reader needs to generate a strong electric field that is then used to inductively power the actual tag.
The problem with energy consumption is exasperated by the fact that the bigger the reader is, and the longer the reading distance is (i.e. distance from the tag), the more power the reader uses. Shrinking the reader so that the reading distance is only about two centimeters (approximately the minimum allowable distance for usefulness of the system to be maintained) does help limit the amount of power used. However, the power required to create the electric field is still extensive, and thus the field cannot be active continuously.
Therefore, in a typical mobile device with short-range communication capabilities the device is prone to require a larger power supply and/or more frequent charging of the power supply, as compared to the mobile device that is not equipped to communicate via a short-range medium. Both larger power supplies and more frequent power supply charging are not viable alternatives in the mobile environment. Larger power supplies lead to larger mobile devices, which is counter-intuitive to the general mobile concept that “smaller is better” or at least more practical. In the same regard, frequent charging of the mobile device power supply is inconvenient for the user and reduces the lifetime expectancy of the power supply.
The intuitive solution to energy management in mobile terminal incorporating short-range systems is to keep the electric field turned off for a majority of the time, and activate, i.e., “wake” the device only on regular intervals. For example, a typical low frequency RFID reader runs on a 3 Hz scan cycle; meaning that it is activated, i.e., “wakes up”, once every 330 ms to check for tags, in the general vicinity. With current technology, this type of repetitive activation can add up to upwards of 20 percent of the power consumed by the mobile device. However, in the vast majority of instances the wake-up period results in no transponders being available, so that the power that is consumed is unwarranted.
As such, there is a need in the industry to conserve the power in mobile devices associated with short-range communication to permit utilization of conventional power supplies and typical power supply charging schedules for the mobile devices. Various attempts have been made to address power management in mobile devices and particularly those devices that are associated with NFC.
One type of power-conserving method has been implemented for RFID short-range communication. The method involves limiting the “reading” of the identification RFID transponder (also referred to as the tag) to only a portion of the transponder/tag, and if the RFID reader identifies that it has previously read the tag based upon the identification portion, the RFID reader does not read the rest of the tag. While this power-conserving method is helpful, the RFID reader still consumes more power than desired and the method does not address the problem of continual active operation.
In another recently developed power conservation method, an appropriate sensor measures the movement of the mobile device and active read operations continue while the movement of the device is unknown. When the movement of the device is identified, however, one or more of the subunits of the device is changed from an active operation mode to a sleep operation mode, where the sleep operation mode consumes less power than the active operation mode. The device then stays in the sleep operation mode while the movement of the device is known, then changes back to the active operation mode when the movement of the device becomes unknown. Again, while this power-conserving method is helpful, the device still consumes more power than desired because the device is in an active operation mode anytime the movement is unknown, which amounts to most of the time that the device is in use due to the “mobile” nature of the device.
In addition to energy management it is also highly beneficial for the user of the mobile terminal to be aware of when the transceiver/reader is in an active reading state. Without knowledge of when the transceiver/reader is active, it is possible for the mobile terminal to unknowingly encounter a transponder and have data associated with the mobile terminal unexpectedly accessed and communicated to unwanted third parties. The obvious solution would be to implement a button, or a soft key, which when activated by the user turns on the transceiver/reader, or have an application internal to the terminal alert the user when the transceiver/reader is active. However, in many instances these solutions are insufficient, in that, the user experience suffers from such extraneous interaction with the device.
Thus, there is a need for techniques that permit greater conservation of power in mobile devices associated with short-range communication so that the mobile device does not need a larger power supply or frequent power supply charging. In addition the preferred method should provide for intuitive use and clear user control, thereby eliminating the likelihood of the transceiver being activated in unwarranted situations.